Why a "Check Engine" light on dash occasionally on a cold start? (1999 car)

Chris J · Post by **Chris J** » Wed Jun 23, 2010 3:39 pm

I have a Subaru Outback automatic, build date Sept 1999

The problem is:
For the last 2 months, only when the engine starts from cold, I get the "Check Engine" warning sign on the dash.

This occurs in roughly 1 in 20 of cold starts, and is not associated with damp or rain - it happens randomly.

The light stays on for up to 1-2 minutes, then goes out.

When the light is on, there is greatly reduced power, in terms of acceleration, particularly in the lower revs. When the light is out, all returns to normal.

When the light is on, the engine idles normally.

I have taken it to a local service guy, who is not a Subaru specialist. He has looked at the onboard computer which shows a knock sensor error, but he can not easily fit that into the symptoms of the car and is reluctant to do work on the car that he is uncertain will give a cure.

It has been suggested that the high tension leads may electrically cause the symptons. Spraying them and connections with WD10 appeared to have helped, but the problem remains.

If you have any thoughts that might suggest a fix I would be interested to hear them!

Thank you for your consideration

Chris

vincentvega · Post by **vincentvega** » Wed Jun 23, 2010 3:49 pm

your knock sensor is cracked. on cold mornings it is probably getting some condensation in it causing it to throw a code.

inspect the knock sensor. if it has any visible cracks, replace it. They are about $140 new from subaru

Chris J · Post by **Chris J** » Wed Jun 23, 2010 3:54 pm

Now that was quick!

Thanks - I will look into that

Chris

Post by **Alex** » Wed Jun 23, 2010 4:25 pm

yes as said above, and it will get gradually worse. My 01 liberty does the identical thing. Ive left it for about a year and now its almost unbearable. Time to bite the bullet and get a new sensor.

Let me know how you go and where you get it from Chris

cheers

alex

YouTube · Post by **El_Freddo** » Wed Jun 23, 2010 9:26 pm

I've seen some pretty ordinary knock sensors since hunting around for parts in the last year! ScoobyRoo has an awesome example in a pic somewhere...

Welcome to the forum!

Cheers

Bennie

AlpineRaven · Post by **AlpineRaven** » Thu Jun 24, 2010 9:15 pm

My Money is on the knock sensor too, mine was cracked last year and wasnt operating properly...
I bought mine from ebay overseas.
Cheers
AP

tony · Post by **tony** » Fri Jun 25, 2010 2:12 am

My Kia is doing the same except when the light is on the engine runs ok, when off it runs a bit ragged for a while then comes good but uses huge fuel.
RAC check showed knock sensor and oxy sensor.
Knock sensor is about $30, oxy about $170.
Will be changing both to make sure, will do knock sensor first as is cheapest.

Chris J · Post by **Chris J** » Tue Jun 29, 2010 5:52 pm

Thanks all

The knock sensor has been changed, and all is good

Chris

Post by **Alex** » Tue Jun 29, 2010 5:53 pm

whered you get it and how much if you dont mind me asking?

alex

Chris J · Post by **Chris J** » Tue Jun 29, 2010 6:00 pm

Hi

Don't mind at all - Subaru dealer fitted, the sensor was billed at $180 AUD plus 30 min labour

Chris

Bogged! · Post by **Bogged!** » Wed Jun 30, 2010 11:09 pm

I love this AUSubaru forum! My Brumby with EJ22 has been doing identical things to that previously mentioned (code 22) ever since I bought the engine, it had been doing it before that too apparently. The bloke who owned the Liberty it was in had the coil pulled off it, there were four new plugs on the floor as well as another AFM aswell as leads, wires etc. too. Didn't think too much of it until recently after fitting it into my Brumby and I've had all sorts of problems with losing power intermittently or sometimes even most of the time, poor idling occaisonally as well. It does go well mostly but drives me nuts with poor running fits

Tried last weekend to track down wiring faults and couldn't find a crook wire anywhere, I knew it was the knock sensor and have unplugged it on occaison but it still threw up the 22 fault, I had mistakenly thought if it was unplugged it would be out of circuit so no fault code,...uh-uhhh! Anyway, after reading this thread decided to fit my spare EJ25 knock sensor, a reset of the ECU and....BINGO! No more light on and purrs like a happy cat.

I would assume from all of this that it had been going into fail safe or limp mode, when not doing that it was developing full power and rocketed away from intersections, roundabouts and up steep hills but would frequently return to it's sick running. Thank you all for this very handy information source forum, very happy now and probably get booked for speeding tomorrow too:mrgreen: Just had a look and eBay have Subaru knock sensors from China starting at about $34 p.p up to about $US 200 odd plus post, cheapest Australian seller is about 110-120 or so. The spare EJ25 sensor I used had a crack in the plastic sheathing too, do they ALL do it? Looks like they do after reading this thread and what's with that stupid cracking black plastic crappo stuff? Do the aftermarket ones do that too? Not much chop if they go west after a short while too:twisted: Cheers.